Well, I hurt my back a few weeks ago and was not able to move the carboys out of the deep chest freezer (a kolsch) so rather than transfer to carboy I just turned the temp down to 32 on the freezer. Well, the temp changed sucked the air lock water into the carboy so I refilled it. Today when I finally went to keg the beer I noticed the air lock was low again, no big deal I thought. well, the beer is partially oxidized. Not so bad I can't drink it but certainly has some of that sherry notes. It is even darker than I expected. I guess I was thinking that at those temps the beer would be alright - guess not. this is one reason I don;t secondary in the carboy. Guess if you do you might invest in a dry air lock.

Would that dry airlock be a true one-way valve? Since water got sucked in there was low pressure in the head space and not enough CO2 from the beer to fill it.

When the airlock prevents air from entering the head space and leaves the head space pressure lower than ambient pressure you have to make sure that the stopper seal is airtight. Otherwise air will still find its way into the head space.

I wonder, to what extend this problem exists with cold crashing a completely fermented beer in the primary. Here the head space CO2 might be at equilibrium with the beer and no more CO2 is created. As the pressure drops CO2 will be absorbed back into the beer and the head space CO2 volume also contracts. As a result air has to move into the head space.

Plenty - this wasn't a secndary. It was a primary. I only "secondary" in kegs. I prefer to call it bright tank though.

Kai - yeah, at the very least I would really worry about carboy breakage.

Blatz - What the hell, man, my wife can't lift a full carboy!!! To be honest, it isn't really that bad yet. Drink it quick and keep it cold. Won't be sending it out though. Plus, my wife probably won't bat an eye while she drinks it. I mostly brew kolsch for her... mostly.

As far as the dry air lock there was an article how to make one in BYO a few years ago with McMasterCarr parts. I'll see if I can find it. Still, nothing beats stainless under pressure.

It happens to the best of us, but lesson learned. Sorry to hear about your back. Back pain is truly a pain, as my chiropractor can attest! At least he drinks better beer since meeting me.

Yeah, I learned my lesson. Call someone to help next time. I had thought about it but figured the beer would be fine. Really though, its not undrinkable. Just not as good as it should have been. And, for me anyway, more core work is in order. I just can't deal with back pain. It's like hitting the brakes in mid-life. Still not fully over it yet. Sucks!

Yep. damn it! I was goingt o wait until it was carbonated to give my impressions. I think I can taste around the flaw. I wasn;t disappointed in the outcome. That said, it was an expensive batch, hop wise. Don't know I will go all FWH on many beers.

Assuming I did the math / science right... and it's been a while so I could be wrong.

If your secondary carboy is filled with 4.75 gal of beer and .25 gal of CO2 then you will lose 10.35 teaspoons of CO2 volume in the headspace and 3 teaspoons of beer volume (neglecting alcohol content and assuming a drop from 60F to 32F).

This is just over a quarter of a cup. Is that enough air going in to oxidize the beer (assuming your airlock doesn't dry out completely as major's did).

What else am I missing in my logic? More gas is dissovled at lower temps? Do you take the whole carboy volume into consideration for CO2 and not just the headspace?

Assuming I did the math / science right... and it's been a while so I could be wrong.

If your secondary carboy is filled with 4.75 gal of beer and .25 gal of CO2 then you will lose 10.35 teaspoons of CO2 volume in the headspace and 3 teaspoons of beer volume (neglecting alcohol content and assuming a drop from 60F to 32F).

This is just over a quarter of a cup. Is that enough air going in to oxidize the beer (assuming your airlock doesn't dry out completely as major's did).

What else am I missing in my logic? More gas is dissovled at lower temps? Do you take the whole carboy volume into consideration for CO2 and not just the headspace?

Man, I don't know about math and all that. I'm a graphic designer for heaven's sake. Here's what I do know. It was about 5.5 gallons of beer and a 7 gallon carboy (two of 'em actually). Lots of head space. The air lock was low and it was this way for at least 2 weeks. I get some sherry notes in the beer. That's the bottom line of it.

I did about 6 batches with FWH just to make sure. I would agree with you. I do not think I will be FWH any beer.I just got kind of harsh lingering bitterns that I did not enjoy.

For me the bitterness was very nice and smooth. No harshness. I liked the beer very well. But I needed 1/2 pound of hops to get the effect and I would rather use magnum at boiling and crystal at the 20 min. mark for the flavoring and use much less hops in the future. Might try a few more tests, we'll see.

What else am I missing in my logic? More gas is dissovled at lower temps? Do you take the whole carboy volume into consideration for CO2 and not just the headspace?

CO2 absorption by the beer is key. At 60 the beer can hold 1.0 volumes of CO2 at atmospheric pressure. At 32 its 1.6 vlumes. This is a difference of ~0.6 volumes. In the end 5 gal of beer had the ability to suck up 3 gallons of CO2. That’s way more than what your head space provides.

Most of the time that may not be an issue since even finished beer is likely to be oversaturated with CO2 (i.e it holds more than is able to hold at its temperature). And there might also be some residual fermentation that still produces CO2.

I transfer my beers (ales and lagers) to corny kegs before they completed fermentation. Then I give them some time to complete fermentation in the closed keg before I cold crash them. Finally the clear beer is transferred to a serving keg. I don’t like carboys for secondary and I also cannot fit as many in my lagering chest.